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Aqueous two-phase emulsion gel systems for zone isolation

a technology of emulsion gel and zone isolation, which is applied in the direction of fluid removal, borehole/well accessories, chemistry apparatus and processes, etc., can solve the problems of less reliable sealing devices, bulky devices, and high cost, and achieves the effect of convenient and accurate delivery

Inactive Publication Date: 2010-04-27
SCHLUMBERGER TECH CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007]The current invention relates to fluids used in treating a subterranean formation, and in particular, the invention relates to the use of water-in-water emulsions as pumpable fluids at the surface forming gels downhole useful in isolating zones of subterranean formations. The invention is an improvement over the existing art by providing an pumpable polymer suspension for easy, accurate delivery with minimum equipment and hydration time, where such suspensions are capable of forming stiff gels in desired placements downhole, also called a “gel packer”.
[0010]Some embodiments of the invention incorporate aqueous two-phase fluid systems. Although not limited to any specific theory or mechanism of operation, it is believed that the “water-in-water emulsion” allows the polymer to be dissolved and hydrated in a water phase without making an excessively viscous liquid. This emulsion may be a phase-separated fluid in which two or more water-soluble polymers are dissolved in water to create a low viscosity mixture. Such a pre-hydrated concentrated solution can be rapidly dispersed into another water stream to continuously make polymer solutions for wellbore treatments. This makes possible, in some aspects, the elimination of the disadvantages of dissolving a polymer powder or using an oil phase.

Problems solved by technology

However, such devices are bulky, expensive, and can be otherwise undesirable.
Further, some portions of the well are not cased and cement lined.
Conventional sealing devices are not easily used in such areas of the wellbore, and the sealing devices which exist for such use, tend to be less reliable, i.e., inflatable packers.
While various systems have been attempted to seal zones of the wellbore using chemicals such as foams, or gels, such materials have been difficult at best to place into the wellbore, because of the high viscosity of such materials or handling and mixing requirements.
High viscosity materials cannot be easily pumped, and many two-part resin systems involve hazardous chemicals such as isocyanate compounds.
Many conventional systems are based on crosslinking chemistry, but these have not been wholly satisfactory in form or delivery.

Method used

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  • Aqueous two-phase emulsion gel systems for zone isolation
  • Aqueous two-phase emulsion gel systems for zone isolation
  • Aqueous two-phase emulsion gel systems for zone isolation

Examples

Experimental program
Comparison scheme
Effect test

example 1

Thermal Activation of a Two-Phase Polymer Solution to become an Elastic Gel

[0041]Experimentally, it has been found that solutions of guar and hydroxypropyl cellulose (HPC) form aqueous phase-separated solutions over a range of polymer concentrations. A phase-separated mixture was formed by simultaneously dissolving 2 wt % dry guar and 2 wt % dry HPC in 100 ml of DI water in a stirred Waring blender. After stirring for approximately an hour, the sample was allowed to rest for an hour to confirm phase separation. The phase-separated solution was then gently stirred by hand to remix the guar-rich and HPC-rich phases.

[0042]The rheology of this mixed two-phase polymer mixture was then measured at 25 C as shown in FIG. 1. The fluid is of sufficiently low viscosity to be easily pourable and pumpable. It is substantially less viscous than the 2% guar solution viscosity shown for comparison in FIG. 1. FIG. 1 illustrates how the presence of the HPC polymer phase dramatically reduces the rheol...

example 2

Thermal Activation of a Gel

[0046]As a second example of thermal activation of a gel, guar was combined with HPC having a molecular weight of approximately 10,000 to make a low viscosity, pumpable mixture. This example was similar to the first example except that the HPC used had a molecular weight which was less by an order of magnitude. The phase diagram for this polymer combination is shown in FIG. 4.

[0047]In FIG. 4, the red line in the phase diagram approximates the binodal for the system. Compositions to the right of the binodal are two phase fluids that will phase separate with time. Because of the phase separation, these fluids are low viscosity formulations that can easily be poured or pumped. Approximately 31% of the fluid volume is filled with a HPC-rich phase that prevent the full guar viscosity from developing. FIG. 5 provides measurements of the guar / HPC mixture at this condition and a comparison with 2% guar alone in water at this temperature. The addition of HPC 10,000...

example 3

Salt Activation of a Two-Phase Polymer Solution to become an Elastic Gel

[0048]A settable fluid was formed, that can set into a gel either by addition of salt or by exposure to increased temperature. Formulation was 2% guar and 2% Methocel®. The salt used in the example was NaCl. FIG. 6 shows the rheology of 2% guar in aqueous solution with 2% HPC10,000. For comparison, the rheology of 2% guar in solution is also shown.

[0049]FIG. 6 shows the effect on the mixture rheology as the temperature is increased from 21 C to 60 C over a 30 minute time period. The rheology has been quantified in FIG. 6 by monitoring the elastic and viscous moduli continuously with a 10% strain oscillation at a frequency of 0.5 Hz. At lower temperatures, the solution behaves as a low viscosity fluid with the viscous modulus being greater than the elastic modulus. As the temperature exceeds the LCST for the HPC10000, the solution changes to behave like an elastic solid with the elastic modulus increasing by near...

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Abstract

A low viscosity wellbore polymer fluid gelling system comprising an aqueous medium and a water-in-water emulsion comprising a plurality of polymers or oligomers, including at least one removable polymer or oligomer, and at least one gelling polymer or oligomer, wherein said fluid has a low viscosity when injected, and the gelling polymer forms a gel downhole which has a storage modulus of at least about 60 Pa after the removable polymer is removed from the fluid. A method of isolating at least one zone of a subterranean formation penetrated by a wellbore includes the steps of preparing a water-in-water emulsion comprising a plurality of polymers or oligomers including at least one removable polymer or oligomer, and at least one gellable polymer or oligomer; and combining the water-in-water emulsion with an aqueous medium to prepare a low viscosity polymer fluid.

Description

BACKGROUND OF THE INVENTION[0001]The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.[0002]This invention relates to fluids used in treating a subterranean formation. In particular, the invention relates to the use of water-in-water emulsions which are low viscosity pumpable liquids on the surface, but which form stiff gels downhole useful for isolation of a zone or zones in subterranean formations.[0003]Various types of fluids are used in operations related to the development and completion of wells that penetrate subterranean formations, and to the production of gaseous and liquid hydrocarbons from natural reservoirs into such wells. These operations include perforating subterranean formations, fracturing subterranean formations, modifying the permeability of subterranean formations, or controlling the production of sand or water from subterranean formations. The fluids employed in these oilfield o...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): E21B33/13C09K8/42
CPCC09K8/508C09K8/514C09K8/501C09K8/88C09K8/5751C09K8/588C09K8/68C09K8/52
Inventor SULLIVAN, PHILIP F.TUSTIN, GARY JOHNCHRISTANTI, YENNYKUBALA, GREGORYDROCHON, BRUNOHUGHES, TREVOR LLOYD
Owner SCHLUMBERGER TECH CORP
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